APPLICATION OF SPECTROSCOPIC ELLIPSOMETRY FOR REAL-TIME CONTROL OF CDTE AND HGCDTE GROWTH IN AN OMCVD SYSTEM

A multi-wavelength in-situ spectroscopic ellipsometer system is described. The hardware can acquire accurate ellipsometric data at 44 wavelengths in less than one second, is simple and compact, and is well suited for in-situ monitoring of chemical vapor deposition. The software used for data analysis is capable of determining the growth rate and composition of the growing layer in real time. These tools were used to study the organometallic chemical vapor deposition of CdTe, HgTe, and HgCdTe on GaAs. We could obtain the dielectric constants of these materials at the growth temperature and also the growth rate and composition of the layers in real time. Feedback control of CdTe growth was performed by connecting an analog control voltage line from the data acquisition/analysis computer to the dimethylcadmium mass flow controller. Using dielectric constants of HgCdTe for two different compositions at the growth temperature, composition control of HgCdTe was attempted in a similar manner.